U.S. Sen. Tom Harkin said Saturday he will not seek a sixth term in 2014, a decision that frees a new generation of Iowa Democrats to seek higher office and eases some of the burden Republicans face in retaking the Senate.

Harkin, chairman of an influential Senate committee, announced his decision during an interview with The Associated Press, and said the move could surprise some.

But the 73-year-old cited his age — he would be 81 at the end of a sixth term — as a factor in the decision, saying it was time to pass the torch he has held for nearly 30 years.

"I just think it's time for me to step aside," Harkin told the AP.

Harkin, first elected in 1984, ranks 7th in seniority, and 4th among majority Democrats. He is chairman of the health, education, labor and pensions committee, and chairman of the largest appropriations subcommittee.

He has long aligned with the Senate's more liberal members, and his signature legislative accomplishment is the 1990 Americans with Disabilities Act. He also served as a key salesman of President Barack Obama's 2010 health care bill to the wary left.

"I'm not saying that giving this up and walking away is easy. It's very tough," Harkin said at his rural Iowa home south of Des Moines. "But I'm not quitting today. I'm not passing the torch sitting down."

Harkin's news defied outward signals. He has $2.7 million in his campaign war chest, second most among members nearing the end of their terms, and was planning a gala fundraiser in Washington, D.C., next month featuring pop star Lady Gaga.

The news creates a rare open Senate seat Iowa. Harkin, Iowa's junior senator, is outranked by Sen. Charles Grassley, who has held the state's other seat since 1980.

Attention will turn immediately to U.S. Rep. Bruce Braley, a fourth-term Democrat from Waterloo. Braley, who was traveling in Iowa Saturday, did not immediately respond to e-mail and telephone requests to his staff by the AP.

Harkin held open the possibility of endorsing a Democrat before the party's primary if the candidate fit the profile of "someone who is progressive, who is a pragmatic progressive."

Although no Republicans have stepped forward, Harkin's news gives the GOP's private huddles new life.

"There are lots of conversations, but it's very early still," said Nick Ryan, an Iowa Republican campaign fundraiser.

U.S. Rep. Tom Latham of Clive is a seasoned Republican congressman, a veteran appropriations committee member and a robust fundraiser who has survived challenges to win 10 consecutive terms. Aides to Latham declined to comment beyond issuing a statement saying the congressman "respects Sen. Harkin's decision (and) looks forward to continuing to work with him."

But with opening a door in Iowa, Harkin has created a potential headache for his party nationally.

Democrats likely would have had the edge in 2014 with the seat, considering Harkin's fundraising prowess and healthy approval. A poll by the Des Moines Register taken last fall showed a majority of Iowans approved of his job performance.

Democrats hold a 55-45 advantage in the Senate, requiring Republicans to gain six seats to win back the chamber. But Democrats have more seats to defend in 2014_20 compared to only 13 for Republicans.

And the president's party historically loses seats in the midterm elections after his re-election. Obama, a Democrat, was re-elected last year.

Democrats will be scrambling to hold onto the seat in GOP-leaning West Virginia, where five-term Democratic Sen. Jay Rockefeller recently announced he would not seek re-election. Republican Rep. Shelley Moore Capito is running for the Senate seat.

Democratic incumbents also face tough re-election races in Arkansas, Louisiana, Montana, North Carolina and Alaska — all states carried by Republican presidential nominee Mitt Romney in November's presidential election.

Since the election, Harkin has stepped up his role as one of the Senate's leading liberal populists.

He was a vocal opponent late last year of President Barack Obama's concession to lift the income threshold for higher taxes to avoid the so-called fiscal cliff. Harkin instead supported raising taxes on all earners making more than $250,000 a year.

He also endorsed Obama's call for banning assault rifles and larger ammunition magazines in the wake of the Connecticut school shooting last month

Despite Harkin's strong political position, he has faced questions about his and his wife Ruth's role in developing a namesake policy institute at Iowa State University, Harkin's alma mater.

The Harkins and their supporters have been pushing for the institute to house papers highlighting his signature achievements, including the ADA and shaping farm policy as the former chairman of the agriculture committee.

In one long-running dispute, they've pressed ISU's president to rescind rules restricting the institute's ability to research agriculture, which Harkin derided as a violation of academic freedom. And Harkin has evaded questions about his role in fundraising for the institute after disclosure reports showed some of its largest donors are firms that have benefited from his policies.

Harkin dismissed that those questions had any bearing on his decision.

RICHMOND, Va. — President Obama launched his bid for a second term Saturday by working to mobilize supporters with a forward-looking message in the face of challenges that include sluggish economic recovery.

The question facing voters, he told a boisterous crowd during the second stop on the official launch of his re-election campaign, isn't whether Americans are better off today than four years ago.  "The real question," he said, is "how we’ll be doing tomorrow."

Obama tried to accomplish this in two ways: Seeking to rekindle the enthusiasm surrounding his 2008 candidacy, and sending stark warnings about what it would mean if his presumptive Republican challenger, Mitt Romney, were elected.

Brendan Smialowski / AFP - Getty Images

President Barack Obama and first lady Michelle Obama wave at a campaign event May 5 in Richmond, Va.

The word ‘Forward’ printed on placards was held by the crowds at both rallies, a kind of 2.0 version of the ‘hope and change’ theme that propelled the Obama campaign in 2008. The crowds at each were loud and enthusiastic, though the Romney campaign was quick to note that the Columbus arena wasn't filled to capacity. Both crowds were heavy on students, and the Richmond rally had a number of African-Americans in attendance, reflecting the area's large black population.

Analysis: Obama re-election launch seeks to define stakes of campaign

Romney spokeswoman Andrea Saul said Saturday: "No matter how many lofty campaign speeches President Obama gives, the fact remains that American families are struggling on his watch: to pay their bills, find a job and keep their homes.”

That statement came because the former Massachusetts governor found himself on the receiving end of a broadside by the president on Saturday, one that took aim at a cornerstone of Romney's campaign, his claim of economic competence.

"When a woman in Iowa shared the story of her financial struggles, he responded with economic theory," Obama said, painting Romney as out-of-touch.

"Corporations aren't people, people are people!" Obama later added, dredging up Romney's quote at the Iowa state fair, when he compared corporations to individuals.

The election may hinge on the economy, but Obama's first formal day of campaigning suggested he won't cede that issue to Romney. He and the first lady both played to broad middle class frustration about diminishing social mobility.

"It's that fundamental promise that no matter who you are or how you started out—if you work hard, you can build a decent life for yourself and yes, an even better life for your kids, and an even better life for your kids," First Lady Michelle Obama said in Columbus.

There was much about Obama's campaign launch that seemed familiar from his 2008 campaign.

He said he was still "fired up" and "ready to go," drawing on a campaign slogan from his last election. His two stops on Saturday were in Columbus, Ohio and Richmond, Va. — the state capitals of two crucial swing states Obama had won against Sen. John McCain. And two staple blocs of Obama's 2008 coalition, those young voters and black voters, showed up in throngs for this weekend's events.

He sought, in no uncertain terms, to draw a line from their effort that year to this fall's campaign, taking strides to remind them of the accomplishments in the meanwhile — his health care law, Wall Street reform, winding down the war in Iraq and killing Osama bin Laden, among other initiatives.

"I didn’t run, and you didn’t work your hearts out, just to win an election," Obama said in Richmond.

He added, toward the end of his remarks: "If people ask you ‘what’s this campaign about?’ you tell them it’s still about hope. You tell them it’s still about change."

But the heady optimism from 2008 has been tempered, namely by an anemic economic recovery. The April jobs report found the U.S. economy added 115,000 jobs last month, falling below expectations and suggesting that the pace of hiring has slowed.

Perhaps in recognition of the new political reality, Obama dropped the gloves versus Romney and sharply criticized the former Massachusetts governor, linking him also to a deeply unpopular Republican House of Representatives.

"For the last few years, the Republicans who run this Congress have insisted that we go right back to the policies that created this mess in the first place," Obama said. "And now, after a long and spirited primary, Republicans in Congress have found a champion — they have found a nominee for president who has promised to rubber-stamp this agenda if he has the chance."

It might not have been the lofty rhetoric that drew so many admirers to Obama in 2008, but these new, sharper themes in this campaign still resonate with the president's most ardent supporters.

"I'm just as enthusiastic as the last time, because I think it's going to be a race between an average joe and a multimillionaire," said Marc René of Richmond, an emigre from Haiti in 1994 who works at a local nonprofit.

"My wife and I work, we have great careers, but we still try to make end's meet. We don't have a net worth of $280 million dollars," he said.

Meaghan Mcinnis of Richmond, a relatively recent college graduate who lost one of her first jobs out of school before finding a new one, attended the rally with her friend Jamie Dalton. Both women said they feared the notion of Republican-led "war on women" aggressively messaged by Democrats.

"I feel like there are much bigger issues, and I don't appreciate that 50 and 60-year-old men are making decisions for my 20-something-year-old body," said Mcinnis.